1. Field of the Invention
The present invention relates to a method for removing phosphorus contained in eutrophic water and a method for reutilizing recovered phosphorus.
2. Description of the Related Art
Conventionally, as one factor for water pollution in enclosed water areas, such as lakes or rivers, there has been elution of phosphorus contained in eutrophic water. As one method for treating eutrophic water by reliably adsorbing such phosphorus, there has been a method that includes introducing an adsorbent such as zeolite into eutrophic water and allowing eutrophic components to be adsorbed thereon, followed by dredging to discharge the eutrophic components out of the water area, as disclosed in, for example, Japanese Patent Application Laid-open No. H9-310373. Also, there has been also a method that includes laying a granulated material of coal ash on the bottom of a water area as a treatment target such as a lake to adsorb phosphorus, as disclosed in, for example, Japanese Patent Application Laid-open No. 2004-113885.
However, the methods disclosed in Japanese Patent Application Laid-open No. H9-310373 and Japanese Patent Application Laid-open No 2004-113885 introduce zeolite or laying a granulated material of coal ash on the bottom, and they have a disadvantage that when the capacity of phosphorus adsorption is reached, the adsorption effect is lost and thus the adsorbent itself such as zeolite or a granulated material of coal ash should be removed by dredging, thus increasing costs such as labor cost. Further, these methods only consider removing phosphorus from eutrophic water, and there is no reference to efficient recovery of phosphorus and effective reutilization of recovered phosphorus.